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OPC: Common Misunderstandings about OPC

by Naeem Ismat (Guest Contributor)  |   December, 2007


Do you know what OPC really stands for…. it does not stand for "Oooh…Please Connect"  and "Old Programmers’ Club." Actually OPC stand for OLE for Process Control (where OLE is Object Linking and Embedding). Some also say Open Process Connectivity, or simply OPC.

When end users or systems integrators move from traditional drivers to OPC servers, sometimes they have confusions about this new piece of software which they are going to add to control system. Here are some of the most common myths:

 

OPC “SERVER” and your New Computer Specifications:

This is one of most common questions asked of me during seminars, training sessions and while working with clients/SIs on systems topology. Most end users, from managers and engineers to guys on the plant floor, seem confused by this name. Actually they try to relate it with IT server class software and then think about server class computers. I have noticed that this name is equally confusing even for IT related staff as, when setting up specs for new projects, they think of it as a SERVER. When we say OPC server it means just another piece of software on your computer. It is NOT like MS Server 2003. It is just like any other computer software/utility. You are going to upgrade/replace your vendor specific driver to a new driver which is now OPC compliant.  This global driver works the same way as your original/old driver used to work for reading and writing data to your controllers. So you can use any computer for your new OPC SERVER. You may have to select a powerful server class computer for your other HMI SCADA or any other software which you are using, but not for OPC server.  So, the PC on which OPC server runs doesn’t have to be a Server class PC. Any standard PC works fine. An OPC server is not itself a heavy application.

OPC “SERVER” Installation:

I also hear many questions like “Does it require special expertise for installation?” “Can I install it and perform setup here in our engineering department or do I need to call our IT?”  A typical OPC server installation is a piece of cake and not like any server class software (W200S or W2003S) installation. Overall installation is very simple and straightforward. Most vendors provide a setup.exe file for OPC server installation. Double click on this file. Normally it prompts for very basic and standard information like installation path, and choice of installing OPC server and/or OPC client.  Hit yes and installation will start. Normally it takes 2-5 min on a “standard” computer. Sometimes, depending on the vendor, installation may prompt you for some additional features and components. In some cases, the vendor’s SCADA software installs the driver during SCADA software installation and you don’t need to install it separately. After installing OPC server, your system can now exchange data with any other third party OPC compliant software.  

OPC and Protocol:
You will be using the same protocol if you are upgrading/replacing your existing old driver with an OPC compliant server. The OPC server does NOT replace your existing protocol; you will still be using your existing protocols which may be Data Highway Plus (DH+), Modbus RTU, ModbusPlus, ModbusEthernet, Profibus or Ethernet/IP.

 

OPC and HMI/SCADA:
The HMI/SCADA systems only have to know one language – “OPC”, which gives you many choices. This is critical for your future needs. No more dependency on your existing old system. If you are not happy with the performance of your current software or support from your vendor and decide to put another vendor’s SCADA software into a new area of the plant instead of sticking with the same vendor, you don’t need to worry about data sharing. All you need to make sure of is that the new software is OPC compliant and you can get any third party OCP server for your old system. Companies like Matrikon, Kepware, and many others offer OPC servers for almost every software and protocols. 

 

Before OPC, there were no standards for interfacing with devices, tools and applications. Each vendor had to develop their own proprietary servers.

With OPC, we have a standard interface enabling applications to communicate and exchange data and objects. Vendors are now developing to one standard OPC interface.

 

Before OPC, we used to have custom interfaces which were costly, inefficient, and risky.
Now with OPC, Client and Server write to a standard, we get reduced costs and protected investments, and we have more choices, which is helping to increase productivity.



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